The 24-floor Grenfell Tower blaze in London last summer cost 71 people their lives and is being probed by a public inquiry. Photo: PAThe 24-floor Grenfell Tower blaze in London last summer cost 71 people their lives and is being probed by a public inquiry. Photo: PA

Grenfell Tower was wrapped in a cladding system that did not comply with building regulations and was incorrectly installed, creating "multiple catastrophic fire-spread routes", a report found.

Dr Barbara Lane, an expert commissioned by the Grenfell Tower inquiry, delivered an excoriating assessment of the refurbishment which finished a year before the fire.

The rainscreen cladding put on the building used material that did not meet fire safety standards, while the system as a whole was not capable of effectively preventing the inferno spreading.

In a report published on Monday, Dr Lane wrote: "There were multiple catastrophic fire-spread routes created by the construction form and construction detailing."

The 24-floor Grenfell Tower blaze in London last summer cost 71 people their lives and is being probed by a public inquiry. Photo: PA

Windows in individual flats had no fire barriers encasing them and these openings were surrounded by combustible material, the expert found.

Such a shortcoming "increased the likelihood of that fire breaking into the large cavities contained within the cladding system" and provided "no means to control the spread of fire and smoke".

The gap beyond the window, in turn, was supposed to have fire-stops at intervals which would halt the advance of flames - but these were installed incorrectly.

There was also no evidence they had ever been tested for performance in the cladding system.

Fire engulfs Grenfell Tower in west London

Any fire which started near a window therefore had a "disproportionately high probability" of spreading into the rainscreen cladding, Dr Lane concluded.

The link between the kitchen window and the rainscreen cladding system on both the column and above the windows was the "primary cause of the early stage of the fire spread", she said.

The cladding itself - Reynobond 55PE - contributed to the "most rapid" of the fire spread, the report said.

Dr Lane said: "The assembly - taken together with the insulation material on the existing external wall, the missing and defective cavity barriers - became part of a successful combustion process."

Five pathways were created through which a fire could spread, meaning each flat was "no longer" a fire-safe box, instead the whole building was at risk.

When a blaze took hold on June 14, it caused multiple internal fires, multiple fires on entrance fire doors and large quantities of polymeric-based smoke which crept into flats and lobbies.

This required smoke-control in multiple lobbies, firefighting efforts on multiple floors and on the exterior of the building, the need for a change of the evacuation strategy and the need for disabled residents to self-evacuate "for which no facilities were provided within the building".

The scale of the cladding's shortcomings never appears to have been grasped by any of the key bodies linked to the refurbishment.

Dr Lane wrote: "I have found no evidence yet that any member of the design team or the construction ascertained the fire performance of the rainscreen cladding system materials, nor understood how the assembly performed in fire.

"I have found no evidence that Building Control were either informed or understood how the assembly would perform in a fire.

"Further I have found no evidence that the (Tenant Management Organisation) risk assessment recorded the fire performance of the rainscreen cladding system, nor have I found evidence that the LFB risk assessment recorded the fire performance of the rainscreen cladding."